The present invention pertains to azeotropic and azeotrope-like compositions of 1,2-dichloro-3,3,3-trifluoropropene (HCFC-1223xd) and hydrogen fluoride.
In recent years there has been universal concern that completely halogenated chlorofluorocarbons (CFC""s) might be detrimental to the Earth""s ozone layer. Consequently, there is a worldwide effort to use fluorine-substituted hydrocarbons that contain fewer or no chlorine substituents. In this regard, 1,1,1,3,3-pentafluoropropane, a hydrofluorocarbon (HFC) having zero ozone depletion potential, is being considered as a replacement for chlorofluorocarbons such as dichlorodifluoromethane in refrigeration systems and trichlorofluoromethane as a blowing agent. The production of HFC""s, i.e. compounds containing only carbon, hydrogen and fluorine has been the subject of interest to provide environmentally desirable products for use as solvents, blowing agents, refrigerants, cleaning agents, aerosol propellants, heat transfer media, dielectrics, fire extinguishing compositions and power cycle working fluids. It is known in the art to produce fluorocarbons such as HFC""s by reacting hydrogen fluoride with various hydrochlorocarbon compounds. Such HFC""s are not only considered to be much more environmentally advantageous than hydrochlorofluorocarbons (HCFC""s) or chlorofluorocarbons (CFC""s) because they are not non-ozone depleting, but also they are also non-flammable, and non-toxic as compared to the chlorine containing compounds.
1,1,1,3,3-Pentafluoropropane (HFC-245fa) is well known in the art as described in U.S. Pat. Nos. 5,496,866 and 5,574,192, both of which are incorporated by reference herein in their entirety.
It has now been found that an intermediate in the production of substantially pure 1,1,1,3,3-pentafluoropropane, is an azeotropic or azeotrope-like mixture of 1,2-dichloro-3,3,3-trifluoropropene (HCFC-1223xd) and hydrogen fluoride. This intermediate, once formed, may thereafter be separated into its component parts by extraction techniques. The azeotropic and azeotrope-like compositions find use as anhydrous (non-aqueous) etchants for etching semiconductors in the electronics industry as well as compositions for removing surface oxidation from metals. After separation from HF, HCFC-1223xd may be used as a pharmaceutical intermediate.
In one embodiment, the invention provides an azeotropic composition consisting essentially of 1,2-dichloro-3,3,3-trifluoropropene and hydrogen fluoride.
The invention further provides an azeotropic or azeotrope-like composition consisting essentially of from about 1 to about 90 weight percent hydrogen fluoride and from about 10 to about 99 weight percent 1,2-dichloro-3,3,3-trifluoropropene, which composition has a boiling point of from about 26xc2x0 C. to about 68xc2x0 C. at a pressure of from about 24 psia to about 84 psia.
In another embodiment, the invention provides a method of forming an azeotropic or azeotrope-like composition, which method comprises blending from about 1 to about 90 weight percent hydrogen fluoride and from about 10 to about 99 weight percent of 1,2-dichloro-3,3,3-trifluoropropene, which composition has a boiling point of from about 26xc2x0 C. to about 68xc2x0 C. at a pressure of from about 24 psia to about 84 psia.
In still another embodiment, the invention provides a process for removing 1,2-dichloro-3,3,3-trifluoropropene from a mixture of 1,2-dichloro-3,3,3-trifluoropropene and at least one impurity, which process comprises adding hydrogen fluoride to the mixture in an amount sufficient to form an azeotropic or azeotrope-like composition of 1,2-dichloro-3,3,3-trifluoropropene and hydrogen fluoride, and thereafter separating the azeotropic composition from the impurity.